Field of the Invention
This invention relates to the field of metal working and more specifically to the field of producing metal sections having uniform properties and uniform structure.
Background of the Invention
Piping and tubing are produced by conventional processes such as casting, extrusion, and strip forming combined with bonding/welding. The main function of piping and tubing is typically to transport material (i.e., a fluid) from one location to another. The material requirements for conventional piping and tubing include strength, leak tightness, and resistance to erosion and chemical attack. Such material requirements for the typical functions are often not demanding or challenging. For instance, the micro-structure of the tubing or piping may not be important. The micro-structure in the pipe or tube may vary from one location to another without serious negative impact.
For instances in which the mechanical requirements for piping and tubing during operations are significant, the micro-structure of the piping and tubing material may often need sufficient characteristics. As an example, the characteristics may include a sufficiently small grain size. The sufficient characteristics may also include sufficiently uniform or consistent micro-structure. Such characteristics may be desired to provide an expected performance during subsequent forming and operation. Significant mechanical requirements may be needed when tubing or piping carry fluid under high pressure or may be formed into another shape (i.e., by hydro-forming). If the tubing or piping contain regions with inferior properties, the operating conditions may be limited by the weak link properties (i.e., characteristics), and forming or operational characteristics may be degraded. Such inferior properties may include those in or near a weld. Both of these factors may influence cost effectiveness. In many cases, the micro-structure across the thickness of the tube wall is non-uniform. Such non-uniformity may result from manufacturing conditions. For instance, in cast metal pipe, the grain size may be smaller near the outside and inside tube wall surfaces. Drawbacks to the non-uniformity may negatively impact tube performance and thus overall cost.
Consequently, there is a need for improved processes for producing tubing and piping. Further needs include improved methods for producing uniform and consistent micro-structures in hollow sections of material.